Conventionally, heat conductive adhesives having adhesive polymer as matrix have been used for bonding a heat generating semiconductor device or electronic component with a heat radiating conductive member. Silver, copper, gold, aluminum, or other metals and alloys having a good heat conductivity, or aluminum oxide, magnesium oxide, silicon oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide or other ceramics, carbon black, graphite, diamond or various other heat conductive fillers are blended in these heat conductive adhesives, in order to enhance the heat conductivity. Among others, electric insulation heat conductive adhesives filled with boron nitride powder, excellent in heat conductivity and electric insulation are used largely.
On the other hand, the Japanese Patent Laid-open No. SHO 62-194653 and the Japanese Patent Laid-open No. SHO 63-62762 disclose adhesion methods for improving the heat conductivity by orienting an adhesive including magnetic substance such as nickel in the magnetic field are disclosed.
However, the boron nitride powder has a heat conductivity in the flake shape thickness direction smaller than a heat conductivity in the surface direction; therefore, an adhesive blending simply boron nitride powder in a polymer could not present a sufficient conductivity as its surface direction is charged in parallel to the thickness direction in the adhesive layer after adhesion.
On the other hand none of adhesion methods of the aforementioned Japanese Patent Laid-open No. SHO 62-194653 or the Japanese Patent Laid open No. SHO 63-62762 could be applied to the application requiring electric insulation for blending electric conductive magnetic metal powder or the like.
In other words, as an adhesion method having a good electric insulation and high heat conductivity has not been developed, a considerable heat generation from semiconductor device or other electric components accelerated the electro-chemical migration or corrosion of wiring or pad portions, the generated heat stress provoked cracking or destruction of composing material, the interface of composing material junctions was peeled off, or other troubles happened in a way to shorten the life of electronic components.
On the other hand, the heat conductive adhesive of the Japanese Patent Laid-open No. 2000-273426 by the Applicant, has diamagnetic filler of 20 W/m·K or more in heat conductivity blended in the adhesive, but boron nitride powder was not taken into account as diamagnetic filler.